An installation of the kind specified performs the double function of evacuating used assemblies from the main reactor vessel and introducing new assemblies into such vessel.
The assemblies involved in such handling are all the assemblies forming the reactor core, such as the fuel assemblies, the lateral neutron screening assemblies and the absorbing assemblies.
In the French Super Phenix reactor the installation for handling the assemblies comprises a transfer hood disposed above the slab surmounting both the main and adjoining vessels, so as to straddle the adjacent edges thereof. Two inclined ramps extend through the slab so as to produce a communication between the transfer hood and a primary station situated inside the main vessel and a secondary station situated inside the adjoining vessel. The transfer hood and ramps have guide rails along which two pots move each of which transports an assembly. The pots are attached to lifting means comprising chains each entrained by a winch disposed in the upper part of the hood.
The installation for handling the assemblies of the Super Phenix reactor operates symmetrically, one of the pots being employed to evacuate a used assembly, while the other pot is employed to introduce a new assembly into the main reactor vessel. When the two points have been remounted inside the transfer hood, the latter performs a rotation of 180.degree. around its vertical axis, so that each of the pots can descend again via the ramp opposite that via which it was introduced into the hood.
In the Super Phenix reactor assembly handling installation, the transfer hood is generally called the "transfer lock". This name is explained by the fact that slide valves are disposed between the hood and each of the ramps, thus enabling the hood to operate like a lock or sluice during the handling of the assemblies. When the reactor is operating, the slide valves are closed so as to ensure the containment of the reactor vessel.
In practice the sluice-like operation of the transfer hood is not used, since the containment of the interior of the main reactor vessel with respect to the adjoining vessel during the handling of the assemblies is performed by a syphon of liquid metal disposed in the lower part of the ramp descending into the adjoining vessel. The only function of the slide valves, therefore, is to ensure the containment of the main reactor vessel during reactor operation.
The presence of the slide valves between the ramps and the transfer hood means that the pot-guiding rails must be interrupted over a length which is considerable in relation to the diameter of the wheels via which the pots move over the rails.
A first consequence of this break caused by the slide valves is that the pots must be given extra wheels to ensure that they continue to be guided when they pass over the break. In addition to the consequent increase in cost, the extra wheels make the guiding of the pot hyperstatic, so that there is the risk that the pot may be jammed in case of the deformation or angular deviation of the ramps.
Moreover, the breaks introduced by the sidevalves must be crossed at low speed, so that the rate of handling is seriously impeded by the presence of these breaks.